There is only one Pokemon that may be broken enough to be quickly banned:

. However, I believe it should not be banned, because if the council plans to test other Pokemon,

might make them irrelevant or

might become more manageable. For example, if Spectrier is tested, it might be broken without

but could be niche with

in the meta. Consequently, if Pokemon such as

or

are tested,

might become more of a niche Pokemon. I believe that most potential unbans should be tested/dropped together as we might end up in a fun/competitive meta where broken checks broken.
speaking of which Pokemon I believe should and should not be tested, I think these can be broken down into three tiers:
tier 1) Should never be tested (less than 2 OU Pokemon or other tier 3 potential unbans can switch into them)
tier 2) Should maybe be tested in the future (2 to 3 OU Pokemon or other tier 3 potential unbans can switch into them)
tier 3) Should definitely be tested (4 or more OU Pokemon or other tier 3 potential unbans can switch into them)
As for tier 1, this would include most box legendaries and Pokemon such as

.
All these Pokemon are broken and should not even be considered for potential testing. (I might be wrong about

)
As for tier 2, I identified 6 Pokemon these are:

:Landorus-Incarnate:

and

. Allow me to explain the potential switch-ins to each.

:

and

can both switch in, however,

's u-turn keeps momentum and will slowly chip away at these mons. therefore even if this mon is tested it will most likely still end up banned.
:Landorous-Incarnate: :

and

can both switch in but gravity will be an easy counter to them and therefore probably would end up banned or not tested

:

and

will all be able to switch into

and with

being nearly on every team and a meta warper I believe

has a chance to be tested and remain in the OU tier.

: Defensive

or

can both switch into

and be able to heal but

might be a centralizing force, that being said with the prevalence of strong Pokemon with priority

might not be too hard for most teams to handle.

:

and

can switch in.

is able to u-turn out to a check and

Powerwhip will scare

out. But

might be too much for OU teams to handle, I think that

will still be banned.

: only water absorb

or an

can switch in, however, if tested it can promote the use of

and

and could therefore not be broken in OU, but z-moves might still push this pokemon over the edge.
Lastly, tier 3, in which I identified 18 potential unbans (a surprisingly large amount of Pokemon) that have 4 or more switch-ins, these Pokemon are

.

: Truly a crap Pokemon carried by rage fist, if rage fist is banned then I don't think this guy will even reach UU, it will most likely be in RUBL. If Rage Fist remains legal it can still be switched on and threatened by

and

. I believe a rage fist

might be healthy for the meta as it means people can't just spam volt-turn moves and actually have to make hard reads, which benefits good players.

:

and

can all switch in. It would promote the use of snow (

) which clearly walls, and could also encourage the use of

that completely walls. Baxcalibur without the Terra is a good Pokemon but not a centralizing force and is not broken.

:

and

all switch in comfortably without taking much damage from STAB, cover moves such as focus blast may be a problem, but a Pokemon that needs focus blast to beate its counters is not broken. That being said with z-fighting this Pokemon might be over the top. Testing this Pokemon is a must in my opinion as the chance of a ban is 50%.

: walled by other psychic types in the tier such as

and walled by

and

. It has knock-off, taunt, and entry hazards but the Pokemon has weak defenses and offenses meaning it either has to be utility or offensive, with only 2 viable type of sets, it will not be hard to deal with, pokemon with better stats, abilities, and typing have the same utility moves such as

and the like.

: a controversial mon but I do believe that the mons in OU can handle it, all of

and

can switch in and either threaten, progress the game-state, or pivot into a check. This is without even considering Pokemon such as

or

. But I still believe that

might be too much of a centralizing force in the meta and will probably end up being banned.

: Without Terra, this Pokemon can no longer muscle past its switch-ins, these include but are not limited to

. I don't even believe this Pokemon can survive UU. pursuit is the bain of this Pokemon's existance.

:

and

all switch into this mon, this is without considering other non-OU mons such as Altaria-Mega and

. It was clearly pushed over the edge by Terra in the previous meta but now can easily be countered and is weak to stealthrocks.

: Ghost types are very annoying for this Pokemon as it usually only runs suckerpunch (as a dark type move) for priority, and is therefore walled by

and Skeledirge which all switch in and either cripple it or beat it outright this is without mentioning Pokemon that switch into a seismic toss and can pivot out such as

. However because the seismic toss-parental bond mechanic is very broken it might prove too strong for the meta, that being said the plethora of fighting-type checks are vast and are on 99.9% of teams, these include

. other potential unbans might such as

and

might also be a problem.

: This Pokemon is strong as it finally has a decent ice move (icicle spear) and dragon dance, but the lack of coverage brings this Pokemon down, steel type pokemon (

) and

can switch in and resist both STABs. The day

gets Earthquake is the day it will remain in UBER with the big boys. That being said its bulk coupled with roost, substitute, and snow can push this Pokemon over the edge. I think it has a fair chance of being banned.

: After looking at

I realised this mon struggles with 4 move syndrome, as no matter the set pokemon in the meta always wall. for example, if this Pokemon does not run a ground or dark move it gets walled by

but if it does, it will not be able to touch Landorous,

and

unless it has ice punch which means

and

wall. In addition, the plethora of fighting types faster/scarfed (

and Zamazenta-Crowned) could handle Lucario-Mega. But I believe Lucario-Mega might be too fast and too strong for the OU meta. This Pokemon needs testing.

: Walled by

and

and is also checked by

and

. This Pokemon would probably be an A-tier but would be manageable by most teams.

: This Pokemon is very strong but I think that there are Pokemon in the meta that can wall and threaten this Pokemon, mainly bulky dragon types (

Altaria-Mega) bulky fire types (

) and is severely walled by pokemon such as

and

since they 4x resist his STAB.

: Without the ability to terra this Pokemon can no longer beat its counters the way it did before. This means that Pokemon such as

and

can easily switch in, in addition to fairy types in general, such as

and

. Plus pokemon with strong super effective priority such as

and

can check it. Faster/scarfed Pokemon can also beat it such as

and

. Bulky offensive Pokemon such as

and

can also come in and take any hit then finish it off.

: Without Terra,

is no longer broken, it might still be good with the terrain-seed combo but it still has clear counters such as

and

. Just the fact that

(the meta-defining Pokemon) is immune to both STABs is a detriment to

and will mean that

will not be as viable as before. In addition to this the fact that a defensive

can switch into any

even if it is +2 means that

is no longer broken.

: This Pokemon is very strong and has good coverage but has no good stat-boosting moves. Not only that, it also suffers from 4 move syndrome, as it wants to run all five of Sunsteel strike, psychic fangs, flare blitz, close combat, and earthquake. Pokemon like

and

all switch in and either beat

or pivot out (with a volt-turn move) into a check. These checks include

and

. I think that

will be more of a defensive Pokemon as it is bulky and has access to moves like knock off, morning sun, teleport, roar, toxic, and thunder wave.

: This Pokemon gets walled by very prominent Pokemon in the meta such as

(does not care about boost, unaware),

(switches into any move),

(pursuit trap), and

. Not only that but

also switches in and

also walls, as it is immune to ghost-type moves and does not care about switching into a will-o-wisp. With

in the meta, this Pokemon might become a niche pick within the meta.

: even though people think this Pokemon is broken as it has STAB heavy slam, it still has clear counters in the meta such as

plus potential

and

. This Pokemon also has to carry an item meaning it will be slower than most booster and scarfed Pokemon. therefore many checks are present in the Meta such as

and

. I personally think that the normal

is better than

as it is free to carry an item such as heavy-duty boots or leftovers to counter this entry hazard meta.

: The true problem with this Pokemon is Glare which leads me to believe that the top four Pokemon that can switch in could be

and

(because it has rest and unaware). Other Pokemon that can switch in but not into a Glare include

and

. I also think that this Pokemon will be hindered due to the presence of strong dragon and fairy types such as

and

. Overall I think

might become too centralizing and might still be banned as Thousand Arrows is an amazing move akin to Rage Fist.